Do you have menu access from the screen then?
Maybe the brightness of your camera monitor is turned way way down (if it can be adjusted), or maybe the monitor has gone bad… But if you can see menu items on it, then it's not the monitor itself but something in between.
Check your menu or user manual to see if there is something about the monitor's brightness.
This is all I can suggest for now. Keep trying until you find it and make sure you tell us what it was.
Good luck.